The owners, unaware of the lump of wood's true value, must have been stumped when the auctioneer recognised it as a rare example of zitan artwork. It is intricately carved from a single piece of wood with images of dozens of figures – a popular Chinese subject known as 'The Hundred Boys'.

It was initially given a guide price of £20,000-£30,000 but interest has since grown to such an extent that it's expected to achieve at least five times that amount.

'We expect our phone bidding lines to be fully booked and we know many Chinese specialists are travelling to our auction room to bid in person,' says Richard Harrison, Sworders' head of Asian art. 'With that level of interest, we could see it realise a sum well into six figures.'